Perforation cleaning method and apparatus



July 14, 1942. c, E. BURT PERFORATIGN CLEANING METHODAND APBARATUS 2sheets-sheet 1 VFiled Jan. 14, 1939 INVENMR vC'Lmwrfwcrs E. .Buer

BY @uw Q. m@

ATTORNEY Mamma u, m.

C. E. BURT July 14, 1942.

PERFORATION CLEANING METHOD'AND APPARATUS 2 Sheets-Shieet 2 Filed Jan.14, 1959 Patented July 14, 1942 PERFRATION CLEANING METHOD AND APPARATUSClarence E. Burt, Los Angeles, Calif., assignor to Baker Oil Tools,Inc., Huntington Park, Calif., a corporation of California ApplicationJanuary 14, 1939, Serial No. 250,966

25 Claims.

loading chamber is initially sealed against ingress of well fiuid by avalve or a fragile sealing means capable of being opened or ruptured, asthe case may be, to permit the hydrostatic pressure of the column offluid in the well to effect a sudden and violent inrush of Well fluidthrough the perforations to clear them of flow restricting materials andcarry such materials into the loading chamber past a back-pressurevalve, after which the cleaner with its entrapped load is removed fromthe well and the contents of the loading chamber is dumped or otherwiseremoved, it being then necessary to recondition the cleaner before itcan again be used. Since perforation cleaners f this general characterare of sufficient capacity to clean only a few feet of well screen at atime,

and since such well screens may be and often are a hundred or more feetin length, it becomes apparent that a relatively large number of roundtrips of the cleaner, with the necessary dumping and reconditioningthereof, is required to complete the cleaning of an entire screen andthat the complete job is a relatively expensive and time consumingundertaking; it will also be evident that as the hydrostatic pressure ofthe fluid column in the well supplies the motivating force producing theflushing action above referred to, this iiushing action of the cleanerwill be directly proportional to its position of use below the iluidlevel of said fluid column and will vary at different elevations in thesame well as well as in different wells having uid columns of differentheights, and may even degenerate into a mere owing action having noflushing value in wells having an exceeding low iluid level or ininstances in which the fluid level has receded to a point relativelyclose to a screen section to be cleaned. Obviously the flushing actionof a hydraulic cleaner of this type is not of uniform character andcannot be varied at will by the operator during a cleaning operation,nor will such a clean-.

er provide the operator with any indication of the success or failure ofthe cleaning operation until the cleaner is removed from the well andthe contents of its loading chamber is examined.

It therefore becomes the principal object of the present invention toprovide an improved method and apparatus which involve a continuouscirculation Wet-tube principle carried into effect through the use of acirculating tubing string provided with packing means for isolating aflushing zone in the well casing adjacent the perforations thereof, andwhich utilizes the velocity of a motivating fluid circulated in thetubing string and in the casing above said Zone to create a suctioninfluence tending to induce a continuous inward flushing flow of wellfluid through the perforations and said zone to clear said perforationsof fiow restricting materials and combine with the circulation streamfor conveyance thereby to the surface; my improved method and apparatusbeing fully capable of conducting a series of successive perforationflushing operations without removing the cleaner from the well andwithout any dumping or reconditioning thereof between the individualflushing operations, thus enabling a complete perforation cleaning jobinvolving all of the perforations of a well casing to be completedduring a single round trip of the cleaner, the circulation providing amedium through which the operator may at all times control the createdsuction inuence to maintain a uniform flushing action at differentelevations or to vary the flushing action at will to compensate for anyvariable conditions encountered, the return circulation providing aconstant visual indicating means keeping the operator fully nformed asto the progress and effectiveness of the ushing operation.

Two forms of embodiment of the present invention are exemplified in thefollowing description and illustrated by way of example in theaccompanying drawings, in which:

Fig. l is a longitudinal section through a screen portion or a wellcasing showing the perforation cleaner of the present invention partlyin section and positioned therein, the parts being illustrated in theirnormal positions.

Fig. 2 is a similar view showing the parts in operated positions.

Fig. 3 is a transverse section taken on the line III-III of Fig. 2.

Fig. 4 is a transverse section taken approximately on the line IV--IV ofFig. 2.

Fig. 5 is a vertical section of the saine general character as Fig. 1,illustrating a second embodiment of the present invention.

Fig. 6 is a similar View showing the apparatus of Fig. 5 in an operatedcondition.

Fig. '7 is a transverse section taken on the line VII--VII of Fig. 6.

Fig. 8 is a transverse section taken on the line VIII- VIII of Fig. 6.

Referring particularly to Figs. l to 4, A designates a casing or linerwhich is assumed to be properly positioned in a well containing a columnof well uid and which is perforated to provide a screen portion B, and Cdesignates the perforation cleaner that has been lowered into saidscreen to a position of use, by means of a tubing string D which, beforethe perforation cleaning operation, will be connected to the usualcirculation pump at the surface.

The perforation cleaner C provides a tubular body structure comprising acirculation discharge unit I screw-threaded at its upper end forconnection to the tubing string D and at its lower end for connection toan upper packer body I I which is joined by a screw-threaded coupling I2and an adjacent pipe length i3 which is connected, preferably byscrew-threads, to the upper end of a pump housing I, said pump housinghaving a screw-thread connection with a lower packer body I 5 that isclosed at its lower end by a rounded guide cap I6 screw-threaded there-An upper packing sleeve Il, formed of rubber or other suitable resilientmaterial, surrounds the upper tubular packer body II and a similar lowerpacking sleeve I8 surrounds the lower tubular packer body I5, each ofsaid packing sleeves being similarly reenforced at opposite ends by ringmembers I9 and 2G, respectively,

and each of said ring members being provided with an internal lipengaging within a companion external groove formed in the respectivepacking sleeve. The lower ring member 29 of each packing sleeve isslidably mounted on its associated packing sleeve I8 is connected in alike manner to the pump housing I4, each packing sleeve thus having anupper end which is secured to the body of the cleaner and a lower endwhich is longitudinally slidable thereon. In back of the upper packingsleeve II, the body member II is provided with lateral ports 2l and inback of the lower packing sleeve I8, the body member I 5 is providedwith similar lateral ports 22. With this arrangement the several bodymembers provide a down-flow passage which communicates with the spacebehind the upper and lower packing sleeves through the respective ports2| and 22, for a purpose which will later be explained.

Fixed by welding or other suitable means within the bore of the tubularpump housing I 4 is a sleeve member 23 having a concentric lower end ofreduced diameter spaced from the wall of said pump housing as at 2d,this annular space 24 communicating with the interior of the lowerpacker body I5 and with the interior of the tubular body member i3 abovethe pump housing, through vertical passageways 25 formed by channels inthe exterior surface of the sleeve 23 and by the interior surface of thepump housing, as shown in Fig. 3, the space 24 and passageways 25forming a portion of the down-flow passage of the cleaner.

Arranged concentrically within the bore of the sleeve member 23 is aVenturi pump nozzle 25 having a restricted throat 27 and provided withsuction orifices 28 disposed immediately above said throat andcommunicating with an annular space 29 formed by an exterior groove insaid nozzle and by the interior surface of said sleeve member, saidsleeve member having upwardly angled suction passages 30 communicatingwith the annular space 2G and with companion suction ports 3I formed inthe wall of the pump housing I4, as shown in Figs. 2 and 4.

The discharge end of the bore of the Venturi pump nozzle 28 iscounterbored to receive the lower end of a pump discharge conduit ortube 32 which extends through the reduced upper portion of the bore ofthe sleeve member 23 and into said counterbore. Said lower end of thedischarge tube 32 is surrounded by suitable packing rings 33 and theVenturi nozzle 26 is removably mounted in sleeve member 23 and heldrigidly in place therein by a screw-threaded bushing 34 which engagessaid nozzle and forces it upwardly to tightly clamp against the packingrings 33 which prevent fluid leakage at this point.

The upper end of the discharge tube 32 is connected to a supportingspider 35, the legs of which are welded or otherwise joined to thedischarge unit Iii and are provided with discharge passages 36communicating with the interior of the discharge tube and with companiondischarge ports 3l formed in the side wall of said discharge unit IG, asshown in Figs. 2 and 3.

In conducting a perforation cleaning operation with the above describedapparatus, the perforation cleaner C is attached to the lower end of thetubing string D and lowered into the well casing A as said string ismade up in the usual manner. During the lowering of the cleaner, wellfluid present in the casing will enter and completely fill all of theopen spaces within the device, and the bore of the tubing string up tothe level of the fluid column.

With the cleaner lowered to a desired position of use within the screento be cleaned, the.

circulation pump at the surface will be connected to the tubing stringand circulation of the motivating fluid will be established, suchmotivat ing fluid preferably being oil if the well is a pro-` ducing oilwell.

The path of the circulation will be down the.-

tubing string past the supporting spider 35, through the upper packerbody II, coupling I2 and pipe I3, through the passages 25 and 24 of thepump housing I and into the lower packer body I8 where it reverses andflows upwardly through the Venturi nozzle 23, the tube 32 and thedischarge passages 36 of the supporting spider to discharge through thedischarge ports 31 into the casing above the upper packer Il.

As an immediate effect of the circulation there will be a rise inpressure in the down-flow passage of the cleaner which will be effectivethrough the lateral ports 2I and 22 to expand the upper and lowerpacking sleeves I'I and i8 to packing engagement with the casing wall,the two packers thus packing 01T the interior of the screen B from therest of the interior of the casing and isolating an intermediateflushing zone E adjaent the perforations to be cleaned, as shown in Withthe packers I'I and I8 thus set in the well casing, the throat orreduced pressure zone of the Venturi pump 26 becomes connected, throughthe suction orifices 28, suction passages 3U, and suction ports 3|, onlywith the flushing zone E between the two packers, and the motivating uidin its flow through the restricted throat -2'! of the Venturi nozzlewill create a suction inuenceproducing a pressure differential whichwill induce a continuous inward flushing flow of well fluid through theperforations and the zone E to clear said perforations of such materialsas may be restricting the flow areas of the several perforations, theflushing well fluid carrying the removed flow restricting materialspassing through the iiushing zone E and the suction ports, passages andorifices of the Venturi pump to combine with the circulation stream forconveyance thereby to the surface.

It will be understood that since the produced suction influence isdirectly proportional to the velocity of the motivating fluid throughthe Venturi pump, the ushing action of the well fluid through the screenperforations will at all times be under control of the operator and mayby him be varied as is desired or is necessary to compensate for anyVariable or diiierent conditions encountered.

The circulation will be continued as long as desired, preferably untilthe operator is assured that the screen section being cleaned is clearand flowing to the full capacity of its several perforations.

My improved method and apparatus provides such assurance while thecleaner is in its position of use, and enables the operator to vary theproduced iiushing action of the apparatus until such assurance is had.

A visual indication of the effectiveness of the perforation flushingaction is provided by the return circulation and in a great number ofinstances a substantially clear return circulation practically devoid offreighted mud, parafiin, shale particles and other foreign perforationclogging materials and carrying no greater sand content than underordinary producing conditions-will at once indicate to the operator areasonably clear condition of the screen section being flushed.

However, there may be conditions under which a clear return circulationmay indicate a completed flushing operation while the volume of thereturn circulation may denote only that the flushing action wassuccessful in iiushing from the perforations merely those cloggingmaterials which could be dislodged by the degree of flushing forceemployed, leaving other clogging materials which require a greaterflushing force to dislodge.

Obviously, since the volume of uid pumped down the tubing string isknown and since all of the flushing fluid which combines with thecirculation stream must come from the ushing zone and through theseveral perforations adjacent said zone, the total volume of fluidpassing through said perforations may be measured as an apparentincrease in the return circulation.

The operator will, of course, know the height of the column of wellfluid above the screen section .being flushed, as well as the flow andsuction capacity of the Venturi pump for any rate of circulation, andthe volume of Well uid that should be drawn in through the perforationsof saidscreen section under normal conditions, and from these knownfactors he can calculate the volume of return circulation increase whichwill denote a-properly cleaned screen section for the circulation rateemployed to produce the suction influence and flushing force involved.

Incase the measured increase of the return circulation in relation tothe volume of the ingoing circulation falls appreciably below thecalculated increase, the operator will at once be informed that,regardless of the clear character of such return circulation, it isreasonably probable that the flow capacity of the screen section isstill restricted by clogging material which could not be dislodged bythe forces previously employed, and he can then increase the circulationpressure until there is produced a degree of suction influencesufficient to create the flushing force necessary to dislodge theremainder of such clogging materials.

When the flushing or cleaning operation is completed at one elevation toclean the perforations of one section of a screen, the circulation willbe stopped to release the two packers, and the cleaner, will, bymanipulation of the tubing string, be translated in the casing to a newposition in an adjacent section of the screen, and the above describedoperation repeated to clean the perforations of said adjacent screensection. Thus, without removing the apparatus from the well, a wellscreen of any length may be cleaned during a single round trip of thecleaner.

It will therefore be evident that the method and apparatus of thepresent invention will effect a great saving in the cost of well screencleaning operations, and that the constant and variable control of theflushing operation exercised by the operator through his control of themotivating circulation fluid, coupled with the visual indicationafforded by the return circulation, will enable the operator to maintainthe apparatus at its maxim im eiciency under any conditions encounteredin the same well or in any other well, in which the apparatus may beused, this being of particular importance in View of the facts thatvarious wells may contain fluid columns of different height and ofdifferent gravity nuids and may have screens of widely diiferentcharacter, particularly as to area and shape of perforations.

Further, in view of the fact that the character of the productiveformations may widely vary in different wells and even at differentdepths in a single well, the controlled motivating circulation enablesthe operator to so govern the flushing action as to eliminate or greatlyreduce danger of breaking down the established oil channels of theproductive formations.

In Figs. 5 to 8 of the drawings there is disclosed a second embodimentof the apparatus of the present invention, elements similar to those ofthe apparatus shown in Figs. 1 to 4 being designated in Figs. 5 to 8 bysimilar reference characters, with an added suffix.

In this embodiment the body structure cornprises a circulation dischargeunit Ia which screws into the upper end of a tubular packer body 4i)having secured Within its lower end, by welding or other suitable means,a partition H which is provided with an axial depending pipe 42 closedat its lower end by a winged guide cap la. Surrounding the tubularpacker body i9 is an upper packing sleeve lia, a lower packing sleeveISa and an intermediate spacing cage member 43 which at opposite ends isprovided with internal lips engaging in companion external groovesformed in the adjacent ends of the respective packing sleeves, said cagethus connecting the lower end of the upper packing sleeve with the upperend of the lower packing sleeve. A reinforcing and anchoring ring 44 hasa similar lip and groove engagement with the upper end of the upperpacking sleeve lia and is rigidly connected, by screws 45 or otherwise,to an external flange 46 formed on the body member 40, while the lowerend of the lower packing sleeve l8a is reinforced by a ring member 47slidable on the body member 40 and having a l'lip and groove engagementwith said sleeve.

A packing expanding cylinder 48 slidably engages the lower end portionof the body member 40 and the depending pipe 42 and is provided withsuitable packing rings 49 and 50 to prevent fluid leakage between saidparts. Said cylinder 48 provides an annular suction chamber whichcommunicates through ports 52, formed in the partition 4l, with theinterior of the body member 40. The body member 40 provides a suctionpassage and secured in its side wall is a flow bean 53 which provides alateral suction port 31a communicating with the annular space 54 behindthe cage member 43, said cage member having a plurality of elongatedopenings 55 formed in its wall, as shown in Fig. 5.

Fixed by welding or other suitable means within the lower portion of thebore of the discharge unit or pump housing Illa is a sleeve 35a havinglateral discharge ports 36a registering with companion discharge ports31a formed in the wall of the housing unit Illa. At its lower end thesleeve 35a has a restricted passageway 56 having a valve seat 57 at thepoint where it tapers upwardly to join the main bore of the sleeve. Aball valve 58 is adapted to be sent down the tubing string at the propertime to engage the seat 51 and block the downway flow of circulationiiuid at this point and insure a full flow of the circulation streamthrough the discharge ports 36a, 31a and into the well casing above theupper packing Ha.

Arranged concentrically within the bore of the unit Ilia above thesleeve 35a is a Venturi pump nozzle 26a, the lower end of which isspaced from the wall of said unit and ts into a counterbore formed inthe upper end of the sleeve 35a with the discharge end of its borecoinciding in diameter with the bore of said sleeve. A bushing 34ahaving an internal diameter coinciding with that of the intake end ofthe nozzle bore, screws into the bore of the sleeve 35a and secures thenozzle in place.

This Venturi nozzle 26a provides a restricted throat 27a and is providedwith suction orifices 28a disposed immediately below said throat andcommunicating with the annular space 29a. between the nozzle and thewall of the pump hous-A ing, which in turn communicates with verticalpassages 33a formed by channels in the exterior surface of the sleeve35a and by the inner wall surface of the housing lila, as shown in Fig.'7, said passages 35a extending downwardly to communicate with theinterior of the body member 40.

In the operation of this apparatus an initial circulation, partlythrough the discharge ports 31a and partly through the passage 56 andthe interior of the body member 4E) and through the port 36a and cageopenings 55, may be had to clear the interior of the casing ifnecessary.

To conduct the perforation cleaning operation, the ball 58 is insertedin the tubing string and is pumped down through the throat of theVenturi nozzle to engage the seat 51 and stop the downward circulationat that point, thus compelling the entire circulation stream todischarge above the upper packer.

The suction influence created by the fluid circulation through theVenturi pump will be effective to reduce the pressure in the body member4l] and in the lower chamber 5| to cause an upward travel of the packingexpanding cylinder 48 which will engage the ring member 41 and translatethe lower packing sleeve 18a, the cage member 43 and the lower endportion of the upper packing sleeve l'la upwardly to compress thepacking sleeves longitudinally so that they will expand radially topacking engagement with the casing wall and isolate the flushing zoneEa.

The perforation cleaning operation will then be conducted in the samemanner as previously described in connection with the apparatus of Figs.1 to 4. In the event the packing sleeves Ha and |811 do not readilydisengage from the casing wall upon stopping the circulation preparatoryto a shifting of the cleaner to a new position in the casing or to aremoval of the cleaner from the well, the operator will take an upwardstrain on the tubing string to loosen the packing sleeves from thecasing so that the inherent resiliency of said sleeves will tend torestore the packers to their normal condition.

While I have shown the apparatus of the present invention in twopreferred forms, it is to be understood that various changes ofstructure may be made by those skilled in the art without departing fromthe spirit of the invention as defined in the appended claims.

Having thus described my invention, what I claim and desire to secure byLetters Patent is:

1. In a method of cleaning a screen or perforated portion of a wellcasing or the like, the steps comprising packing off the interior of thecasing to dei-ine a flushing zone adjacent the perforations to becleaned, circulating a motivating iiuid to discharge in the casing abovesaid zone to produce a suction inuence, and utilizing such suctioninfluence to reduce the pressure in said zone and induce an inwardiushing ow of well fluid through the perforations and said zone to clearsaid periorations of ilow restricting materials.

2. In a method of cleaning a screen or perforated portion of a wellcasing or the like, the steps comprising packing off the interior of thecasing to define a ushing zone adjacent the perforations to be cleaned,circulating a motivating fluid to discharge in the casing above saidzone to produce a suction iniiuence, utilizing such suction influence toreduce the pressure in said zone and induce an inward flushing ow ofwell fluid through the perforations and said zone to clear saidperforations of ow restricting materials, and controlling thecirculation to regulate the produced suction iniiuence and governiiushing action.

3. In a method of cleaning a screen or perforated portion of a wellcasing or the like, the steps comprising packing off the interior of thecasing at relatively spaced points to dene an intermediate flushing zoneadjacent the perforations to be cleaned, circulating a, motivating fluidto discharge in the casing above the upper packing point to produce asuction inuence, and utilizing such suction influence to reduce thepressure in said zone and induce an inward iiushing iiow of well fluidthrough the perforations and said zone to clear said perforations of owrestricting materials.

4. In a method of cleaning a screen or perforated portion of a wellcasing or the like, the

steps comprising packing off the interior of the casing at relativelyspaced points* to'dene an intermediate' flushing zone adjacent theperforations to be cleaned, circulating a motivating `fluid to discharge.in the casing above the upper forated portion of a well casing or thelike, the

steps comprisingV lowering into 'said casing a string of pipe carryingpacking meansv and provided with a suction pump discharging above saidpacking means, circulating va motivating fluid 'through said pump tolcreate a suction influence, and utilizing such suction influence tocause said packing means-to pack off the interior Vofsaid casingandVdenne a flushing zone adjacent theperforations to be cleaned and toreduce the pressure in said zone and induce an inward flushing fiow ofwell fluid through the perforations and said zone to clear saidperforations-offlow restricting materials.

6. vInl amethod of cleaning a screenv or. perforated portion of awellcasing or the like, the, steps comprising lowering into said casing astring of pipe carrying relatively spaced packers and provided with asuction pump `discharging above the upper packer, circulating amotivating fluid through said pump to create a suction in- "fluence, andutilizing such suction influence to cause said packers to expand andpack off 'the interior of the casing to define an intermediate fiushingzone adjacent the perforations' to be cleaned and to reduce the pressurein said zone and induce an inward ushing flow of well iiuid through theperforations and said zone to clear saidperforations of flow restrictingmaterials.

'7.Y A'fluid-circul'ating method of cleaning perforations formed in awell casing which comprises lowering into'the casing a circulationstring of pipe, packing off the interior of said casing to define aflushingzone adjacent the perforations to be cleaned, circulating amotivating uiddown said circulation string to discharge into the wellcasing above said pack off and create a suction influence tending toreduce the pressure in said Zone and induce an inward flushing ow ofwell fluid through the perforations and said zone to vclear saidperforations of flow restricting materials and combine with thecirculation stream for conveyance thereby to the surface.

8. A iiuid-circulating methodv of cleaning perforations performed in awell casing which comprises lowering `into the casingY a circulationstring-vof pipe, packing'off the interior of said casing to'dene aflushing zone adjacent the perforations to be cleaned, circulating amotivating fluid down lsc-,id'circulation string 'to discharge into thewell casing above said pack off and create a suction influence tendingto reduce the pressure in said zone and induce an inward flushing flowof well fluid through the perforations 'and Vsaid zone to clear saidperforations of fiow restricting materials and combine with thecirculation stream for conveyance thereby to the surface, andvregulating the circulation to regulate the produced suction influenceand govern flushing action.

9. A lfluid-circulating method of cleaning an entire well screeninvolving only a single round trip into the -well of a circulationtubing string, said method including packing off the interior of thescreen to define a flushing zone adjacent the perforations of a sectionof said screen, circulating a motivating fluid down said tubing stringto discharge above said pack ofi" and create a suction inuence,utilizing said suction influence to reduce the pressure in said zone andinduce an inward flushing flow of well fluid through the perforations ofsaid screen section and through said zone to clear said perforations offlow restricting materials and combine with the circulation stream forconveyance :thereby to the surface, stopping such circulation, translat-Ytrip into the well of a circulation tubing string,

said method including packing off the ,interior of the screen to deneaflushingzone adjacent the perforations of a section of said screen,vcirculating a motivating fluid down said tubing "string to dischargeyabove said pack off and create a suction influence, utilizing saidsuction inuence to reduce the pressure in said zone and induce` aninward `iiushing Vflow of kwell uid through the perforations of saidscreen section and through said zone to clear said perforations of flowrestricting materials and combine with the circulation streamforconveyance thereby to the surface, stopping such circulation,translating the tubing string to avproper-,elevation to pack off theadjacent section of the screen, -reestablishing the circulation torepeatthe above dened perforation flushing operation, repeating theabovedeflned cycle yuntil the entire screen is cleaned, and vregulatingthe circulation to regulate the produced suction iniiuence andindependently govern the'iiushingV action -at each screen section.

l1.` A perforation cleaning apparatus having packing means adapted topack oif a well casing to isolate a ushing zone adjacent theperforations to be cleaned, and means for circulating a motivatingfluidin the casing above said zone to create a suction influence tendingto effect a pressure reduction lin said zone and induce an inwardflushing of well fluid through-the perfcrations and said zone to clearsaid perforations of ow restricting materials.

i2. A perforation cleaning apparatus having packing means adapted topack off a well casing to isolate a flushing zone adjacent ltheperforations to be cleaned, and means for circulating a u motivatingfluid in the casing above said zone andv including a suction Apumphaving a suction voriice communicating with said flushing zone,

such pump functioning to induce an inward posed above the upper of saidpackers and a suction port disposed between said packers, and a suctionpump disposed in said flow passage to receive said motivating fluid anddischarge through said discharge port and having a suction orificecommunicating with said suction port.

14. In an apparatus of the character disclosed, the combination of abody adapted for attachment to the lower end of a tubing string downwhich a motivating fluid may be pumped, relatively spaced packerscarried by said body and adapted to be expanded by liuid pressure, saidbody providing a iiow passage to receive the motivating fluid and havinga discharge port disposed above the upper of said packers and a suctionport disposed between said packers, and a suction pump comprising a ownozzle disposed in said flow passage to receive said motivating iiuidand discharge through said discharge port and having a suction oricecommunicating with said suction port.

15. In an apparatus of the character disclosed, the combination of abody adapted for attachment to the lower end of a tubing string downwhich a motivating fluid may be pumped, relatively spaced packerscarried by said body and adapted to be expanded by fluid pressure, saidbody providing a ow passage to receive the motivating fluid and having adischarge port disposed above the upper of said packers and a suctionport disposed between said packers, and a suction pump comprising aVenturi nozzle disposed in said flow passage to receive said motivatingfluid and discharge through .said discharge port and having a suctionorifice communicating with said suction port.

16. In an apparatus of the character disclosed, the combination of abody adapted for attachment to the lower end of a tubing string downwhich a motivating fluid may be pumped, said body having a flow passagedisposed to receive said motivating fluid and an annular valve seat atthe lower end of said passage, said body also having a lateral dischargeport communicating with said passage, vertically spaced packers carriedby said body below said discharge port, a suction pump having a suctionorice and comprising a flow nozzle disposed axially in said flowpassage, said body having a suction port between said packers, meansestablishing fluid communication between said suction port and saidsuction oriiice, and a valving element adapted to be sent down thetubing string to engage said seat and close said flow passage to causethe entire now of motivating fluid to discharge through said lateraldischarge port.

17. In an apparatus of the character disclosed, the combination of abody adapted for attachment to the lower end of a tubing string downwhich a motivating uid can be pumped, said body having a flow passagedisposed to receive said motivating fluid and an annular valve seat atthe lower end of said passage, said body also having a lateral dischargeport communicating with said passage, vertically spaced packers carriedby said body below said discharge port, a suction pump having a suctionorifice and comprising a Venturi nozzle disposed axially in said flowpassage, said body having a suction port between said packers, meansestablishing uid communication between said suction port and saidsuction orifice, and a valving element adapted to be sent down thetubing string to engage said seat and close said flow passage to causethe entire flow of motivating fluid to discharge through said lateraldischarge port.

18. In an apparatus of the character disclosed, the combination of abody adapted for attachment to the lower end of a tubing string downwhich a motivating uid can be pumped, said body having a flow passagedisposed to receive said motivating fluid and an annular valve seat atthe lower end of said passage, said body also having a lateral dischargeport communicating with said passage, vertically spaced packers carriedby said body below said discharge port, a suction pump having a suctionorifice and comprising a flow nozzle disposed axially in said flowpassage, said body having a suction port between said packers, meansestablishing fluid communication between said suction port and saidsuction orifice, a valving element adapted to be sent down the tubingstring to engage said seat and close said flow passage to cause theentire flow of motivating fluid to discharge through said lateraldischarge port, and pressure actuated means rendered effective by thesuction influence of said suction pump to expand said packers.

19. A method of cleaning a screen or perforated portion of a well casingor the like which comprises placing restrictions in said casing to forma flushing zone adjacent the perforations to be cleaned, graduallycreating and thereafter maintaining a desired suction influence for adesired time interval, and applying such suction influence to said zonefrom the beginning of its creation to the end of said time interval.

20. A fluid-circulating method of cleaning a screen or perforatedportion of a well casing or the like which comprises placingrestrictions in said casing to form a flushing zone adjacent theperforations to be cleaned, circulating a motivating fluid in saidcasing to gradually create and thereafter maintain a desired suctioninfluence with the continuation of such circulation, and applying suchsuction influence to said zone from the beginning to the end of suchcirculation.

21. A fluid-circulating method of cleaning a screen or perforatedportion of a well casing or the like which comprises placingrestrictions in said casing to form a flushing zone adjacent to theperforations to be cleaned, circulating a motivating fluid in saidcasing to gradually create and thereafter maintain a desired suctioninfluence with the continuation of such circulation, applying suchsuction influence to said zone from the beginning to the end of suchcirculation, and controlling the circulation to regulate said suctioninfluence.

22. A perforation cleaning apparatus having packing means adapted topack off a Well casing to isolate a flushing zone adjacent theperforations to be cleaned, and means for circulating a motivating fluidin the casing above said zone comprising a venturi having a throatcommunicating with said flushing zone, said venturi functioning toinduce an inward flushing flow of well uid through the perforations andsaid zone to clear said perforations of flow restricting materials.

23. A perforation cleaning apparatus adapted to be lowered in a wellcasing on a tubular string and having packing means cooperable with saidcasing to isolate a flushing zone adjacent casing perforations to becleaned, and means for creating a suction influence in said zone toinduce an inward flushing flow of well uid through said perforationscomprising a suction pump for receiving a motivating uid passingdownwardly through said tubular string for discharge into the casingabove said ushing Zone, said suction pump having a suction orificecommunicating with said flushing zone.

24. A perforation cleaning apparatus adapted to be lowered in a wellcasing on a tubular string and having packing means cooperable with saidcasing to isolate a ushing Zone adjacent casing perforations to becleaned, and means for creating a suction influence in said zone toinduce an inward flow of Well uid through said perforations comprising aventuri for receiving a motivating fluid passing downwardly through saidtubular string for discharge into the casing above said flushing zone,said venturi having a throat communicating` with said flushing zone.

25. In an apparatus of the character disclosed, the combination of abody adapted for attachment to the lower end of a tubular string downwhich a motivating fluid may be pumped, spaced packers carried by saidbody for sealing engagement with a well casing, said body providing aflow passage to receive the motivating uid and having a discharge portdisposed above the upper of said packers and a suction port between saidpackers, and a venturi disposed in said flow passage to receive saidmotivating huid and discharge through said discharge port and having athroat communicating with said suction port.

CLARENCE E. BURT.

